As a standard of a 4th Generation (4G) telecommunications system, International Mobile Telecommunications-Advanced (IMT-Advanced) proposes a higher requirement for performance of the system, and particularly has a higher requirement for uplink and downlink frequency efficiency. Recently, Coordinated Multi-Point transmission/reception (COMP) is constantly concerned and studied as a hotspot technique of the IMT-Advanced.
The COMP technique is a technique which improves coverage of high rate transmission, cell edge service quality and throughput, and system throughput, and is an important technique of improving system spectrum utilization ratio. The so called COMP, namely coordinate transmission by multiple base stations, servers one or more User Equipments (UEs). The COMP defined by a 3rd Generation Partnership Project (3GPP) includes two scenes: one scene is multi-point coordination scheduling, namely coordinating interference among transmitted signals of cells by interactively scheduling information between adjacent nodes; another scene is multi-point joint processing, namely providing jointly a service to a target UE by sharing data, Channel Situation Information (CSI), scheduled information, and etc. among multiple coordinate points.
An advantage of the multi-point coordinated scheduling is that it is unnecessary to interact too much information between nodes, and there is no influence on a wireless interface; a disadvantage is that coordinated transmission gain cannot be obtained, and there is no contribution to improvement of spectrum utilization ratio. An advantage of the multi-point joint processing is that macro diversity and coordinated transmission gain and advanced antenna processing gain can be obtained; the disadvantage is a lot of interaction between data information and CSI information is required to be performed, and complexity is high.
Signal interference may be generated among multiple cells, as shown in FIG. 1, three adjacent cells are separately a cell 1, a cell 2, and a cell 3, and a first UE 1, a second UE 2, and a third UE 3 separately belong to the cell 1, the cell 2 and the cell 3. Signals sent by a base station of the cell 2 and a base station of the cell 3 may interfere the UE in the cell 1, the signals sent by base stations of the cell 1 and the cell 3 may interfere the UE in the cell 2, and the signals sent by base stations of the cell 1 and the cell 2 may interfere the UE in the cell 3.
Currently, an inter-cell multi-antenna coordination technique, namely the COMP technique, is generally adopted to reduce inter-cell signal interference; the inter-cell multi-antenna coordination technique usually includes that: UE measures channel information of a main signal and channel information of an interference signal, and sends the channel information to a base station to which the UE belongs; the base station to which the UE belongs sends the channel information of the interference signal to an adjacent base station; the adjacent base station determines a space in which the interference is small according to interference channel information, and the base station to which the UE belongs sends a signal in the determined space in which the interference is small.
The inter-cell multi-antenna coordination technique includes a step of UE feeding back channel information to A base station to which the UE belongs. However, since data quantity of the channel information is large, in order to reduce transmitted data quantity, the UE generally needs to perform codebook processing on the channel information, and does not directly feed back all of the channel information. The codebook processing is referred to matching the channel information obtained by channel estimation with a codeword vector in a codebook table, and taking an index corresponding to a best matched (most relevant) codeword vector as feedback information, wherein a R8 codebook table shown in FIG. 2 may be adopted as the codebook table. There are two types of feedback information, namely a Worst Codeword Index (WCI) and a Best Codeword Index (BCI), which separately correspond to a maximum interference codeword and a minimum interference codeword.
Although the codebook processing reduces feedback information quantity, accuracy of channel information is also reduced, resulting in channel information distortion. A lot of research shows that: codebook precision, particularly the codebook precision of an interference channel, has a great influence on COMP performance, for example when channel information is integrated, many COMP algorithms may make the COMP performance to obtain a higher gain, and have a very good effect of eliminating interference; but in the circumstance that codebook processing is performed on channel information, COMP algorithms may make the COMP performance to obtain only a smaller gain, even no gain, and the effect of eliminating interference is bad.
Currently, the following two methods are mainly adopted to improve codebook precision of channel information: one method is to expand codebook capacity, another method is to feed back multiple codewords (such as two codewords which are separately a most relevant codeword and a second most relevant codeword), and a base station side combines the received multiple codewords into one vector.
With regard to the method of expanding codebook capacity, since the characteristic of a channel space is not known and only mean quantization can be performed in a multi-dimensional space, therefore the method of expanding codebook capacity can improve codebook precision of the channel information in some scenes, but cannot improve codebook precision of the channel information in some other scenes. Whether the codebook precision of channel information can be improved or not has a strong relevance with the scene, so the codebook precision of the channel information cannot be improved stably.
With regard to the method of feeding back multiple codewords, since each codeword has a relatively big quantization error, multiple codewords may generate a bigger accumulated error, and the codebook precision of channel information cannot be effectively improved, as shown in FIG. 3.
Both the above two methods cannot effectively improve the codebook precision of channel information, therefore COMP gain cannot be effectively improved, a good effect of eliminating interference cannot be reached.